1. Field of the Invention
The present invention relates to fluid refrigeration compositions comprising a hydrocarbon lubricant, a refrigerant immiscible with the hydrocarbon lubricant, and an additive capable of reducing the interfacial tension between the hydrocarbon lubricant and the immiscible refrigerant. More particularly this invention comprises a fluid refrigeration composition comprising a naphthenic mineral oil lubricant, a hydrofluorocarbon refrigerant immiscible with the napthenic mineral oil lubricant, and a surfactant capable of reducing the interfacial tension between the napthenic mineral oil lubricant and the hydrofluorocarbon refrigerant.
2. Description of Related Art
The implementation of the Montreal Protocol to reduce the production of ozone-depleting CFC""s (Chlorinated Fluorocarbons) has led the refrigeration and air-conditioning industry to use HFC""s (Hydrogenated Fluorocarbons, or xe2x80x9cHydrofluorocarbonxe2x80x9d) as alternative refrigerants to the fully halogenated chlorofluorocarbons, such as R12, or the hydrochlorofluorocarbons, such as R-22 (hydrochlorodifluoromethane). Historically, the refrigeration lubricants of choice for CFC""s, e.g., R12 and R22, were purified naphthenic base oils because they were completely miscible in these refrigerants and had good low temperature properties. The traditional view was that the refrigerant and lubricant must be miscible to facilitate lubricant return to the sump of the compressor. The belief is that, immiscibility or poor dispersability between the refrigerant and lubricant at unit operating temperatures may provide unsuitable oil return to the compressor This causes improper heat transfer due to oil coating of the inner surface of the heat exchange coils, and in extreme cases, lubricant starvation of the compressor. The former causes energy efficiency losses, and the latter results in unit burn-out.
The naphthenic mineral oil lubricants that have been used widely in the past are not miscible with the new HFC""s such as, R-134a (1,1,1,2-tetrafluoroethane), R-152a (1,1-difluoroethane), R-32 (difluoromethane), R-143a (1,1,1-trifluorethane), R-125 (1,1,1,2,2-pentafluoroethane), and azeotropic and zeotropic blends consisting of any one of these, or other, HFC components, for example, R 407C, which is a blend of R-32, R-134a and R-125, and R 410A, which is a blend of R32 and R125. This has led to the development of synthetic refrigeration lubricants, such as polyalkylene glycols for use with R134a in automotive air conditioning, or specific short chain polyol esters and polyvinyl ethers for use with R407C and R410A. See, for example, Yamamoto et al., Tribology Transactions, 44-2:209-21 (2001); Sundaresan et al., Proc. Int. Refrig. Conf. Of Purdue U. 6th Annual (1996) pp. 187-192; and Gopalnarayanan et al., Proc. Int. Refrig. Conf. Of Purdue U.8th Annual (2000) pp. 233-240.
U.S. Pat. No. 5,792,383 discloses fluid refrigeration compositions comprising a hydrocarbon lubricant, an immiscible refrigerant and an additive capable of reducing the interfacial tension between the hydrocarbon lubricant and refrigerant.
U.S. Pat. No. 6,074,573 (see also EP 0 908 509 A1) discloses a refrigerator oil composition comprising at least one base oil selected from mineral oils and synthetic oils, and at least one polyoxyethylene-type nonionic surfactant. The composition is said to have an excellent lubricating property, while specifically improving the lubricity between aluminum materials and steel materials. This is said to be effective for preventing such materials from being seized and worn, and suitable as a lubricating oil in refrigerators using hydrogen-containing HFC refrigerants, such as R134a, that do not cause environmental pollution.
U.S. Pat. No. 6,193,906 discloses a refrigerating oil composition which is said to exhibit excellent lubrication properties when used in combination with certain types of coolant, such as a hydrofluorocarbon coolant, which may serve as substitutes for chlorofluorocarbon coolants which have been implicated as causing environmental problems. The refrigerating oil composition is obtained by incorporating, into a component (A); i.e., a base oil containing a synthetic oil, a component (B); i.e, a polyalkylene glycol derivative of formula (I) having a number average molecular weight of 200-3,000: R1xe2x80x94(OR2)mxe2x80x94(OR3)nxe2x80x94OR4(I) wherein R1 and R4 represent C1-C30 hydrocarbon groups, etc.; R2 represents a C2-C4 alkylene group; R3 represents a C2-C30 alkylene group; m and n are numbers that satisfy the above-described molecular weight conditions, wherein n may be 0; and at least one of R1, R3, and R4 has a hydrocarbon group having six or more carbon atoms.
U.S. Pat. No. 6,475,405 discloses a lubricating oil for compression-type refrigerator comprising, as a main component, a polyoxyalkyleneglycol derivative represented by the general formula: R1[(OR2)mOR3]n wherein symbols are as defined in the specification. The lubricating oil is said to have a favorable compatibility with refrigerants and an excellent lubricating property, and is utilized as the lubricating oil for compression-type refrigerator employing hydrogencontaining fluorocarbon compound refrigerants including R-134a or fluorocarbon compound refrigerants without hydrogen.
The disclosures of the foregoing are incorporated herein by reference in their entirety.
A general object of this invention is to provide refrigeration fluid compositions comprising a naphthenic mineral oil lubricant and a hydrofluorocarbon refrigerant immiscible with the lubricant. Other objects appear hereinafter.
It has now been found that the objects of this invention can be obtained with refrigeration fluid compositions comprising a naphthenic mineral oil lubricant and a hydrofluorocarbon refrigerant immiscible with the lubricant, and an effective amount of a specific class of nonionic surfactants.
For purposes of this invention, the term xe2x80x9cimmisciblexe2x80x9d means that a two-phase system is formed between refrigerant and lubricant, at least at any point in the typical operating range of xe2x88x9240xc2x0 C. to 80xc2x0 C. in refrigeration or air conditioning systems.
More particularly, the present invention is directed to a fluid refrigeration composition comprising a naphthenic mineral oil lubricant, a hydrofluorocarbon refrigerant that is immiscible with the naphthenic mineral oil lubricant, and an effective amount of at least one nonionic surfactant wherein said surfactant has a Hydrophilic-Lipophilic Balance in the range of from about 9.8 to about 11.8, is completely soluble in the naphthenic mineral oil lubricant, and has a low pour point; and wherein the blend of surfactant and lubricant is completely clear and transparent and has a low pour point.